The proposed research will characterize neuromotor performance (e.g., neuromuscular abnormalities and/or motor control dysfunction) in Spasmodic Dysphonia (SD) through studies of the acoustic, aerodynamic, kinematic and electromyographic (EMG) manifestations. Experiments are designed to determine: (1) whether neuromotor performance abnormality in SD is limited to laryngeal function or diffusely represented within the speech production mechanism, (2) relations between neuromotor performance abnormality and vocal/speech task (i.e., simple, vegetative or complex, linguistic); and (3) whether neuromotor performance abnormality is associated predominately with initiation of motor acts, execution of motor acts, or both. To accomplish these ends, 20 SD subjects and 10 age- and sex- matched controls who have previously undergone extensive CNS evaluation (as per NIH/NINCDS grant NS 18276-04), will participate in experimental sessions progressing from non- invasive, aerodynamic and acoustic to invasive, kinematic, and vocal tract EMG. By incorporating tasks common to all sessions, we hope to elucidate relations between EMG activity, kinematic events, aerodynamic phenomena, and acoustic/perceptual characteristics of neuromotor performance in SD. Finally, in utilizing this unique, well-studied population of SD subjects, we intend to explore relations between peripheral neuromotor performance and CNS findings in the same subject(s).